Use this page to set the initialization parameters that control the way the database manages its memory usage. You can choose from two basic approaches to memory management:
Select Typical to create a database with minimal configuration or user input. This option is sufficient for most environments and for Oracle Database administrators (DBAs) who are inexperienced with advanced database creation procedures. You can adjust the slider control to allocate Memory Size (SGA and PGA) from a continuous range of values. The minimum value of memory that must be alloted is 250 MB, the default value for all machines. You can move the slider to the right to increase the value of memory size. The maximum value that can be set is equal to the total available physical memory in the machine.
The Percentage field represents the percentage of your total available system memory that will be allocated to the Oracle Database. Based on this value, the Database Configuration Assistant automatically allocates the most efficient amount of memory to the database memory structures.
To allow the Oracle instance to automatically manage instance memory, most platforms require you to set only the initialization parameter MEMORY_TARGET. To do this, select Use Automatic Memory Management. If you select this option, memory is managed automatically, i.e the database instance will manage SGA and PGA size automatically.
If you clear the Automatic Memory Management checkbox, the instance tunes to the value of Memory Size (SGA and PGA), redistributing memory between the system global area (SGA) and aggregate program global area (PGA aggregate). The Memory Size (SGA and PGA) initialization parameter is dynamic; you can change it any time, without restarting the database. You can click Show Memory Distribution button to see the memory allocated to SGA and PGA.
The following platforms support Automatic Memory Management:
For more information about the memory structures within an Oracle Database instance, see Oracle Database Concepts.
If you are an experienced database administrator and you want more control over the allocation of memory for the Oracle Database, select Custom.
To allocate specific amounts of memory to the SGA and PGA, select the Memory Management option as Automatic Shared Memory Management, and specify the appropriate values.
The following table describes the System Global Area (SGA) and Program Global Area (PGA), as well as the initialization parameter for each of these.
| Memory Structure | Description | Initialization Parameter |
|---|---|---|
| System Global Area (SGA) | A shared memory region that contains data and control information for one Oracle instance. Oracle allocates the SGA when an instance starts and deallocates it when the instance shuts down. Each instance has its own SGA. |
SGA_TARGET |
| Program Global Area (PGA) | A memory buffer that contains data and control information for a server process. A PGA is created by the Oracle Database when a server process is started. The information in a PGA depends on the Oracle configuration. | PGA_AGGREGATE |
To customize how the memory is distributed among the SGA memory substructures, select Manual Shared Memory Management, and enter specific values for each SGA subcomponent.
The following table lists a description of each SGA subcomponent, as well as the corresponding initialization parameter for each of these settings. You can review and modify these initialization parameters later in the Database Configuration Assistant.
| SGA Subcomponent | Description | Initialization Parameter |
|---|---|---|
| Shared Pool | Enter the size in bytes of the area for shared SQL and PL/SQL statements or accept the default entry. Large values improve performance in multi-user systems. Small values use less memory. Note: If you installed the Oracle Multimedia and Advanced Replication options, the value for Shared Pool Size must be at least 15MB. |
SHARED_POOL_SIZE |
| Buffer Cache | Enter the size in bytes for the database buffer cache. This is the portion of the SGA that holds copies of data blocks read from data files.The initialization parameter specifies the number of buffers in the database buffer cache. Each buffer in the cache is the size of one Oracle data block (which is specified by the initialization parameter DB_BLOCK_SIZE); therefore, each database buffer in the cache can hold a single data block read from a data file. All user processes concurrently connected to the instance share access to the database buffer cache. |
DB_CACHE_SIZE |
| Java Pool | Java pool memory is used in server memory for all session-specific Java code and data within the JVM. | JAVA_POOL_SIZE |
| Large Pool | Enter the size in bytes for the large pool allocation heap. The Large Pool allocation heap is used by the Shared Server for session memory, by Parallel Execution for message buffers, and by Backup for disk I/O buffers. If is left unset and the pool is required by parallel execution, then Oracle will compute a value automatically. The computation will add 250k per session for the shared server if MTS_DISPATCHERS is configured. A final computation will add a port-specific amount of memory for Backup I/O buffers. Warning: This default computation can yield a size that is either too large to allocate or causes performance problems. In that case, you should set LARGE_POOL_SIZE to a number sufficiently small so that the database can start. |
LARGE_POOL_SIZE |
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